PHP Detecting if source image url link leads to a “broken” image?

Question

Suppose you have a thumbnail generator script that accepts source images in the form of a URL. Is there a way to detect if the source URL is \"broken\" - whether nonexistent

Answer 1

The only really reliable way is to request the image using file_get_contents(), and finding out its image type using getimagesize().

Only if getimagesize() returns a valid file type, can you rely that it is in fact a valid image.

This is quite resource heavy, though.

You could consider not doing any server-side checks at all, and adding an onerror JavaScript event to the finished image resource: